In recent years, as one of treatment methods of ophthalmic diseases that are abnormal in eye lens such as cataract, a method has been increasingly used throughout the world, comprising steps of removing eye lens contents from a capsular sac and inserting an artificially produced intraocular lens into their space.
In the case of the insertion of the intraocular lens, the intraocular lens may give an opaque sight to patients instead of their own natural eye lens. However, regardless of its many advantages, the intraocular lens has problems that a capsular sac into which the intraocular lens is inserted is contracted after the insertion of the intraocular lens.
Accordingly, a new method has been increasingly used, comprising steps of inserting a capsular tension ring into an equatorial region of a capsular sac prior to the insertion of the intraocular lens and fixing the intraocular lens in the capsular tension ring.
A capsular tension ring, which is referred to as open or closed ring formations, is effective in partially relieving contraction of a capsular sac, partially maintaining a shape of the capsular sac from which an eye lens is removed, and easily supporting the inserted intraocular lens.
In order to use a capsular tension ring in a more effective manner, there have been recently ardent studies to develop a structure for easily inserting a capsular tension ring, a structure for preventing a posterior capsular opacity, etc.
However, a more serious problem in the conventional surgical operation of insertion of an intraocular lens is that an anterior capsule and a posterior capsule of a capsular sac are adhere to each other after the surgical operation, which leads to the loss of its inherent function to control a thickness of an eye lens by relaxing and contracting zonule of Zinn.
That is to say, the problems is that a patient does not ensure a sight through active three-dimensional movements of an intraocular lens along objects to be seen, but ensures a passive sight according to the predetermined power of an intraocular lens.
Hereinafter, the conventional surgical operation of insertion of an intraocular lens will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a human eyeball, and FIG. 2 is a cross-sectional view showing a structure of a natural eye lens. Referring to FIGS. 1 and 2, a cornea 10 is a transparent avascular tissue disposed in the outermost region of the eye and protects an eyeball. Also, the cornea serves to reflect the light together with the eye lens. An iris 20 functions as the iris of a camera by adjusting the intensity of the light entering the eye. Also, a pupil 30 is a hole in the center of the iris 20, and adjusts the intensity of the light entering the retina 40 by contracting the hole under the bright light and expanding the hole under the dark light.
An eye lens 50 is a colorless and transparent avascular structure having a convex lens shape in both sides, and arranged in the back of the iris 20. The eye lens 50 is an organ that takes part in reflecting the light entering the eye together with the cornea 10, and its shape is changed according to the contraction and relaxation of a ciliaris muscle 60 and a zonule of Zinn 70 coupled to the ciliaris muscle 60.
Presbyopia is a state that the hardness of the eye lens 50 increases with the age, and therefore the shape of the eye lens 50 is not changed even if the ciliaris muscle 60 contracts, and the cataract is a disease that the eye lens 50 becomes opaque with the age.
The eye lens 50 is filled inside a capsular sac 80, and the capsular sac 80 is composed of an anterior capsule 80a and a posterior capsule 80b, each of which is in contact with an anterior surface 51 and a posterior surface 55 of the eye lens 50. At this time, the anterior surface 51 and the posterior surface 55 of the eye lens 50 are coupled to each other in an equator (E). Each of the anterior surface 51 and the posterior surface 55 is divided into a central region (a) and an equatorial region (b) according to the distance from the equator (E). The central region (a) of the anterior surface 51 has a smaller curvature than the central region (a) of the posterior surface 55, and the equatorial region (b) of the anterior surface 51 has a larger curvature than the equatorial region (b) of the posterior surface 55.
The zonule of Zinn 70 is coupled along an edge of the capsular sac 80. The zonule of Zinn 70 is a kind of a fibrous tissue that couples the capsular sac 80 to the ciliaris muscle 60, and composed of a first zonule portion coupled to the center of the equatorial region in which the anterior capsule 80a and the posterior capsule 80b of the capsular sac 80 meets; and a second zonule portion coupled to a circumference of the equatorial region.
FIG. 3 and FIG. 4 are illustrative views showing an interaction of a zonule of Zinn, an eye lens and a capsular sac when focused on a long distance and a short distance object, respectively. In this application, a Y direction represents a visual axis direction of an eye lens, and an X direction represents an equatorial direction of an eye lens. The visual axis direction of the eye lens means a direction that the light enters an eye lens 50 through a pupil, and the equatorial direction means a direction that, as a vertical direction of the visual axis direction, connects a point that an anterior capsule and a posterior capsule of an eye lens meets.
In the zonule of Zinn 70, a first zonule portion 73 coupled to the center of the equatorial region of the capsular sac 80 is pulled taut and a second zonule portion 71 coupled to the circumference of the equatorial region of the capsular sac 80 is relaxed when focused on a long distance object. As a result, the capsular sac 80 is extended in an X direction of the eye lens 50, and therefore the eye lens 50 arranged inside the capsular sac 80 is extended in the same direction (X).
In the zonule of Zinn 70, the first zonule portion 73 coupled to the center of the equatorial region of the capsular sac 80 is relaxed and the second zonule portion 71 coupled to the circumference of the equatorial region of the capsular sac 80 is pulled taut when focused on a short distance object. As a result, the capsular sac 80 is projected in a Y direction of the eye lens 50, and therefore the eye lens 50 arranged inside the capsular sac 80 is extended in the same direction. As described above, the capsular sac 80 having a natural eye lens disposed therein is coupled to the zonule of Zinn 70, and therefore takes part in actively deforming shapes of the natural eye lens, but the use of the conventional intraocular lens and capsular tension ring forces the capsular sac to contract, which leads to the substantial loss of its functions.
In particular, a ciliaris muscle, which is coupled to a zonule of Zinn to take part in the shape deformation of an eye lens, is a visceral muscle that maintains the endless function to the death. Therefore, the conventional method of artificially removing an ability of healthy ciliaris muscle must be improved in that an ability of ciliaris muscle is not damaged although the eye lens is damaged.
Meanwhile, the conventional intraocular lens and capsular tension ring are disclosed in various literatures including U.S. Patent Publication Nos. 2006/0244904, 2006/0001186 and 2003/0149479.